A GIS Approach to Model Sediment Reduction Susceptibility of Mixed Sand and Gravel Beaches

The morphological form of mixed sand and gravel beaches is distinct, and the process/response system and complex dynamics of these beaches are not well understood. Process response models developed for pure sand or gravel beaches cannot be directly applied to these beaches. The Canterbury Bight coastline is apparently abundantly supplied with sediments from large rivers and coastal alluvial cliffs, but a large part of this coastline is experiencing long-term erosion. Sediment budget models provide little evidence to suggest sediments are stored within this system. Current sediment budget models inadequately quantify and account for the processes responsible for the patterns of erosion and accretion of this coastline. We outline a new method to extrapolate from laboratory experiments to the field using a geographical information system approach to model sediment reduction susceptibility for the Canterbury Bight. Sediment samples from ten representative sites were tumbled in a concrete mixer for an equivalent distance of 40 km. From the textural mixture and weight loss over 40 km tumbling, we applied regression techniques to generate a predictive equation for Sediment Reduction Susceptibility (SRS). We used Inverse Distance Weighting (IDW) to extrapolate the results from fifty-five sites with data on textural sediment composition to field locations with no data along the Canterbury Bight, creating a continuous sediment reductions susceptibility surface. Isolines of regular SRS intervals were then derived from the continuous surface to create a contour map of sediment reductions susceptibility for the Canterbury Bight. Results highlighted the variability in SRS along this coastline.     

PCR-DGGE技术在城市污水化学生物絮凝处理中的特点

通过PCR-DGGE等分子生物学技术可以不经过常规培养直接从活性污泥和生物膜样品中提取DNA,对16Sr DNA V3区进行PCR扩增,结合DGGE(变性梯度凝胶电泳),从而分析活性污泥与生物膜中微生物种群结构.研究证实,活性污泥培养前后微生物种群结构发生很大的改变.同时对2种污水处理工艺中微生物种群结构进行了对比研究,对同一反应器不同位置微生物分布以及不同工况下的微生物种群结构进行了初步探讨.测定了活性污泥中部分菌种的16S rDNA V3区片段序列,通过NCBI(美国国立生物技术信息中心)基因库比对,初步确定细菌的属.结果显示,PCR-DGGE结合测序技术是一种完全可行的快速进行环境学样品微生物研究的分析方法.     

Analysis of the effects diclofenac has on Japanese medaka (Oryzias latipes) using real-time PCR

The expression levels of cytochrome P450 1A, p53 and vitellogenin were investigated in three different tissues of male medaka fish after exposure to diclofenac that is one of the main concerns among pharmaceuticals frequently found in sewage treatment plant (STP) effluents. The results showed that cytochrome P450 1A, p53 and vitellogenin were highly expressed in tissue-specific gene expression patterns after exposure to 8 mg/l and 1 μg/l of diclofenac. These elevated expression levels of three biomarkers suggested that diclofenac has potential to cause cellular toxicity, p53-related genotoxicity and estrogenic effects. It is also noteworthy that diclofenac has the potential to cause these effects even at an environmentally relevant concentration of diclofenac, 1 μg/l.     

甘蔗蔗糖磷酸合成酶SPSⅡ cDNA片段克隆与表达分析

蔗糖磷酸合成酶(Sucrose phosphate synthase,SPS)是蔗糖合成途径的关键限速酶,在蔗糖积累和碳分配中具有重要作用.在茎组织中SPSⅡ表达量占SPS转录总量的40%,表明SPSⅡ cDNA的克隆与表达对蔗茎中蔗糖的积累有着重要的影响.通过RT-PCR技术克隆分离SPSⅡ基因cDNA片段.序列分析表明该cDNA片段包含1个3 183 bp的开放读码框,可编码1 060个氨基酸.GenBank登录号为EU269038.通过实时荧光定量PCR检测SPSⅡ基因在甘蔗糖分积累的不同时期、不同组织部位的相对表达量.结果表明,在糖分积累初期蔗茎中的SPSⅡ相对表达量最大,在糖分积累中期蔗叶中的SPSⅡ相对表达量达到最高峰;同组织部位中,糖分积累初期SPSⅡ相对表达量高于糖分积累中期、后期.图6参11     

Potential dissemination mechanism of the tetC gene in Aeromonas media from the aerobic biofilm reactor under oxytetracycline stresses

The tetC gene has been found to be one of the most widely distributed tetracycline resistance (tet) genes in various environmental niches, but the detailed dissemination mechanisms are still largely unknown. In the present study, 11 tetC-containing Aeromonas media strains were isolated from an aerobic biofilm reactor under oxytetracycline stresses, and the genome of one strain was sequenced using the PacBio RSII sequencing approach to reveal the genetic environment of tetC. The tetC gene was carried by an IS26 composite transposon, named Tn6434. The tetC-carrying Tn6434 structure was detected in all of the A. media strains either in a novel plasmid pAeme2 (n=9) or other DNA molecules (n=2) by PCR screening. The NCBI database searching result shows that this structure was also present in the plasmids or chromosomes of other 13 genera, indicating the transferability of Tn6434. Inverse PCR and sequencing confirmed that Tn6434 can form a circular intermediate and is able to incorporate into a preexisting IS26 element, suggesting that Tn6434 might be responsible for the dissemination of tetC between different DNA molecules. This study will be helpful in uncovering the spread mechanism of tet genes in water environments.     

Single-cell sequencing and mini-sequencing for preimplantation genetic diagnosis

There is increasing interest in the use of preimplantation genetic diagnosis (PGD) as an alternative to routine prenatal diagnosis. However, the costs associated with development and testing of new PGD protocols have forced some PGD centres to limit the number of diseases for which PGD is offered. One of the main factors in the design of new protocols, which affects cost and accuracy, is the choice of the mutation-detection technique. We have assessed the reliability of DNA sequencing and mini-sequencing for clinical diagnosis at the single-cell level and have found them to be rapid and accurate. Extensive optimisation for individual mutations is not usually necessary when employing these versatile techniques and consequently a smaller investment of time and resources should be required during development of new protocols. Additionally, we report single-cell protocols for the diagnoses of cystic fibrosis, sickle cell anaemia and β-thalassaemia, which utilise mini-sequencing. Unlike most mutation-detection techniques, mini-sequencing permits analysis of very small DNA fragments. Small amplicons experience low allele dropout (ADO) rates, and consequently this approach could potentially improve the reliability of PGD. Copyright © 2003 John Wiley & Sons, Ltd.     

Real-time PCR with molecular beacons provides a highly accurate assay for detection of Tay-Sachs alleles in single cells

The results presented here provide the first single-cell genetic assay for Tay-Sachs disease based on real-time PCR. Individual lymphoblasts were lysed with an optimized lysis buffer and assayed using one pair of primers that amplifies both the wild type and 1278 + TATC Tay-Sachs alleles. The resulting amplicons were detected in real time with two molecular beacons each with a different colored fluorochrome. The kinetics of amplicon accumulation generate objective criteria by which to evaluate the validity of each reaction. The assay had an overall utility of 95%, based on the detection of at least one signal in 235 of the 248 attempted tests and an efficiency of 97%, as 7 of the 235 samples were excluded from further analysis for objective quantitative reasons. The accuracy of the assay was 99.1%, because 228 of 230 samples gave signals consistent with the genotype of the cells. Only two of the 135 heterozygous samples were allele drop-outs, a rate far lower than previously reported for single-cell Tay-Sachs assays using conventional methods of PCR. Copyright © 2002 John Wiley & Sons, Ltd.